1. Field of Invention.
The present invention relates to information delivery services, and in particular to the control and specification of program quality supplied to service users in a wireless local storage and playback broadcast system.
2. Related Art.
In many audio playback systems the selected audio programs are delivered on a physical medium, such as compact disk (CD), analog tape (e.g., cassette), or removable semiconductor memory (e.g., SmartMedia(copyright) card manufactured by Toshiba Corporation, Memory Stick(copyright) by Sony Corporation, or CompactFlash(copyright) by Sandisk Corporation). The likelihood of successful program playback is high as long as the storage medium is undamaged. Alternatively, in certain types of information delivery systems audio programs are broadcast for live playback using media such as commercial amplitude and frequency modulated (AM, FM) radio or television signals. The likelihood of high quality playback using broadcast signals is proportional to the quality of signal reception. The larger the distance between transmitter and receiver, for example, the lower the likelihood of acceptable playback quality. For instance, in a typical commercial radio live (direct) broadcast system, users (listeners) are likely to tune to another broadcast station when subjective playback quality becomes unacceptable.
Another communications system alternative is to broadcast audio programs to a mobile receiver for local storage (e.g., in the receiver) and subsequent playback. Quality of service becomes an issue in any broadcast system, however, and so it is desirable to provide methods that determine and control quality of service especially suitable for a broadcast system with local storage and playback.
In a local storage and playback broadcast system, quality of service standards ensure that received programs will not be played to the user unless the stored program meets certain threshold standards. These quality of service standards are set by the broadcast system service provider so that the output satisfies users"" minimum subjective quality standards. Ideally the subjective quality standard is tailored to each program, and the quality standard can be updated to suit listener preferences.
A wireless (radio) system in accordance with this disclosure thus includes a computer database of stored audio, video, and other programs that are broadcast to audio/video-on-demand receivers having local storage capability. Programs are partitioned prior to broadcast into one or more segments. Each segment is a logically coherent unit, such as a song or a particular news story. Programs are digitally encoded and broadcast as fixed length data units (packets). Each receiver captures the broadcast packets, reassembles the captured packets into their associated segments, and reassembles the segments to create the program that is then locally stored in the receiver memory.
Received segments are evaluated at the receiver against quality of service threshold standards to determine if the segments are usable for later playback. One segment quality of service evaluation requires that a minimum fraction (percent) of the packets associated with the segment be usable. Another quality of service evaluation requires that no more than a maximum number of consecutive packets in the segment be unusable.
Programs are output (played) to the user from the receiver""s local storage only after passing one or more additional quality of service evaluations. One program quality of service evaluation requires that a minimum fraction (percent) of the segments associated with the program be usable. Another program quality of service evaluation requires that the first, last, or both first and last segments in a program be usable.
The user""s receiver is configured to carry out these quality of service evaluations. The receiver includes a logic unit, a receiver unit, and a memory to provide the local storage. Once captured, segments and programs are evaluated against quality of service parameters stored in a separate part of the memory. In some embodiments the stored quality of service parameters are updated in response to data received in part of one of the received programs. In some embodiments particular quality of service parameters are associated with particular programs.